The city of Austin, Texas buys about 870 tons/year of fluosilicic acid at a cost of $134/ton. It comes as a 20-30% solution in water.
Last year the city pumped 41.3 billion gallons of water. The fluoride content is said to vary from 0.7-1.2 ppm, which checks with these figures pretty closely, as well as their lab report. (Does everyone know that a US federal law mandates that your water provider (if of sufficient size) must send you an annual report on the quality of the water, including analyses for many pesticides, fluoride, some organic compounds, and certain inorganics? The first reports came out last Oct. but should be still available on request.)
The amount of treated (and fluoridated) water returned to the river here is about 26 billion gallons, around 63%. Storm water run off and infiltration may also be treated for a total of 34 billion gallons. The standard used to design a water system in the U.S. used to be (30 yrs. ago) based on 100 gal/day/person for those in houses, much less for apartment dwellers. Now it may be 2-6 times more, depending on the kind of development.
Ed Groth III (Environment 17(3):29-38 1974?) reviews fluoride as a pollutant and cites a 1964 study of 56 cities in Calif. That study showed domestic sewage already contained more fluoride than what was naturally present or added for dental heath; a tentative guess was that food was the source of the excess, but toothpastes "and other sources" would be negligible.
Cheers, JJ Jacobson